This would not be the measuring-stick weekend series to end all measuring-stick weekend series for the Mets. But they were facing a playoff-positioned team in the Pirates, not the punching bag Marlins or the soup can Rockies.

And as far as series starts go, well, the Mets have had better nights.

“Outside of the 10th inning, that was a very good ball game,” manager Terry Collins said.

But that 10th inning, when reliever Bobby Parnell faced three men, surrendered three hits and left to a round of boos, was fairly awful.

So, the Mets proved they are mortal at home as their seven-game Citi Field winning streak, and an overall run of four straight victories, came to an end in 3-2, 10-inning loss to the Pirates, who claimed first blood in a potentially revealing series.

Parnell (1-2), admittedly “trying to do too much,” was charged with two runs, but the Mets made it interesting in the bottom of the 10th, pushing across a run. But with the bases empty, Yoenis Cespedes, who had homered earlier, struck out and Juan Uribe bounced out to end the game.

“I never lose my hope,” Cespedes said through an interpreter. “I never put my guard down until they get the last out.”

The Pirates, who swept the Mets during a three-game series in Pittsburgh in late May when they outscored them 21-4, delivered three straight hits against Parnell to start the 10th. The third hit, by Gregory Polanco, put the Pirates up, 2-1, and drove Parnell from the game. Aramis Ramirez added a sac fly to make it 3-1.

Juan Lagares opened the home 10th with a double to right, went to third on a wild pitch by Mark Melancon and scored on Curtis Granderson’s sacrifice fly.

“We made a run at them in the bottom of the 10th,” Collins said. “I thought Grandy hit his ball better than that. I thought it was going to get over his head, but it didn’t.”

“Thought it was a good hit, but I didn’t think I had enough to get it out,” So, when Melancon survived and earned his 36th save, to make a winner of Arquimedes Caminero (3-1), the Mets were left to fret over wasted effort and opportunity.

They received a solid seven innings from starter Bartolo Colon who gave up a solo homer to the second batter of the game, Neil Walker, but kept the Pirates off the scoreboard after that.

“I was trying to get ahead in the count and the pitch kind of ran inside to his kitchen where he likes it and he put on a good swing and hit it out,” said Colon (five hits, two walks, seven strikeouts), who has won only one of his last 10 starts.

But the biggest waste may have come in the third inning, when a Lagares single and Granderson double had runners on second and third with no one. Pirates starter J.A. Happ struck out Cespedes, got Uribe on a pop out and struck out Daniel Murphy.

“That game got away in the third inning. That’s where we had to score,” Collins said. “I certainly would have lost a big bet that we wouldn’t have scored a run that inning with those two guys coming up especially against a left-hand pitcher.

“You’ve got to accept the fact it’s baseball and tip your hat when the pitcher makes some pitches and gets two of your big hitters out.”

Said Cespedes: “Believe me, it doesn’t feel great. We’re all trying to do our job, trying hard but we didn’t execute.”

Cespedes did in his subsequent at bat, leading off the sixth. He sent a 2-2 fastball over the wall in left to tie the game, 1-1, with his 20th homer of the season, and his second with the Mets.

“At the moment, it felt great, but we lost, so it was insignificant,” said Cespedes, after the Mets fell to 42-19 at home, still the second best home record in baseball behind only St. Louis (43-17).